Pitchblende mineralization was studied in the younger granite samples collected from Gabal Gattar, north Eastern Desert, Egypt using electron scanning microscope (ESM) and electron probe microanalyses (EPMA). This stu...Pitchblende mineralization was studied in the younger granite samples collected from Gabal Gattar, north Eastern Desert, Egypt using electron scanning microscope (ESM) and electron probe microanalyses (EPMA). This study revealed that this pitchblende contains significant Zr content reaching up to (66.80% ZrO2), which suggests that volcanic rocks were probably the source of such a deposit. High level emplaced high-K Calc-alkaline plutons as Qattar granite may have been associated with their volcanic equivalent emplaced in the surrounding area or now eroded. Lead content of the pitchblende mineralization is high and with moderate volcanics (up to 7.71% PbO). In contrast, it is low in ThO2, Y2O3 and REE2O3. High Zr and Pb content associated with pitchblende mineralization from Gattar granite indicates that the source of this mineralization derived from volcanic magma not from granitic magma. According to the calculation of U-Pb chemical ages using U, Th and Pb content measured with an electron microprobe for this pitchblende yielded ages within 543 - 657 Ma indicating a Pan-African age for this mineralization. This is the first time that a Pan-African age (543 to 657 Ma) is recorded for a U-mineralization in Gabal Gattar younger granite in the north Eastern Desert, Egypt.展开更多
This study analyzed the composition and uranium valence of pitchblendes sampled from the hydrothermal Guidong and Zhuguang uranium deposits of the middle Nanling metallogenic belt, Southern China using X-ray photoelec...This study analyzed the composition and uranium valence of pitchblendes sampled from the hydrothermal Guidong and Zhuguang uranium deposits of the middle Nanling metallogenic belt, Southern China using X-ray photoelectron spectroscopy(XPS).A revolutionary discovery is that the uranium not only exists in the forms of tetravalent and hexavalent uranium oxides, but also occurs in the form of native uranium.This is the first discovery of the existence of native uranium in nature.It greatly helps to reveal the origin of hydrothermal mineralization of uranium, and also has great significance for studying the thermal energy, formation and evolution of the earth.展开更多
An experimental study on reduction of U (VI) by anaerobic bacteria, Shewanella putrefaciens, is first reported here in China. The experimental conditions were: 35℃ and pH = 7.0—7.4, corresponding to a physicochemica...An experimental study on reduction of U (VI) by anaerobic bacteria, Shewanella putrefaciens, is first reported here in China. The experimental conditions were: 35℃ and pH = 7.0—7.4, corresponding to a physicochemical environments in which the sandstone-hosted in- terlayer oxidation-zone type uranium deposit formed in Northwest China’s Xinjiang. Bacteria adopted in the present experiment, Shewanella putrefaciens, occur extensively in natural envi- ronment. Our study shows that nano-crystal precipitates of uraninite quickly occurred on the surface of the cells within one week. It was found that the pitchblende was characterized by a random arrangement of uraninite nanocrystals (2—4 nm) in it, significantly different from natural pitchblende in which uraninite nanocrystals are arranged in order. Finally, a possible mechanism of uranium biomineralization by microorganisms in the deposits is discussed. Our investigation may supply a technical train of thoughts for bioremediation of nuclear-contaminated water envi- ronments and for underground dissolving extraction of the sandstone-hosted uranium ores.展开更多
文摘Pitchblende mineralization was studied in the younger granite samples collected from Gabal Gattar, north Eastern Desert, Egypt using electron scanning microscope (ESM) and electron probe microanalyses (EPMA). This study revealed that this pitchblende contains significant Zr content reaching up to (66.80% ZrO2), which suggests that volcanic rocks were probably the source of such a deposit. High level emplaced high-K Calc-alkaline plutons as Qattar granite may have been associated with their volcanic equivalent emplaced in the surrounding area or now eroded. Lead content of the pitchblende mineralization is high and with moderate volcanics (up to 7.71% PbO). In contrast, it is low in ThO2, Y2O3 and REE2O3. High Zr and Pb content associated with pitchblende mineralization from Gattar granite indicates that the source of this mineralization derived from volcanic magma not from granitic magma. According to the calculation of U-Pb chemical ages using U, Th and Pb content measured with an electron microprobe for this pitchblende yielded ages within 543 - 657 Ma indicating a Pan-African age for this mineralization. This is the first time that a Pan-African age (543 to 657 Ma) is recorded for a U-mineralization in Gabal Gattar younger granite in the north Eastern Desert, Egypt.
文摘This study analyzed the composition and uranium valence of pitchblendes sampled from the hydrothermal Guidong and Zhuguang uranium deposits of the middle Nanling metallogenic belt, Southern China using X-ray photoelectron spectroscopy(XPS).A revolutionary discovery is that the uranium not only exists in the forms of tetravalent and hexavalent uranium oxides, but also occurs in the form of native uranium.This is the first discovery of the existence of native uranium in nature.It greatly helps to reveal the origin of hydrothermal mineralization of uranium, and also has great significance for studying the thermal energy, formation and evolution of the earth.
基金supported by the National Natural Science Foundation of China CNNSFCXGant Nos.40025209 and 40173031)the International Coopenative Research Foundation of NNSFC(Grant No 2002-40210104086)Ph.D.Base Foundation of Education Mimistry of China(Grant No.20020284036).
文摘An experimental study on reduction of U (VI) by anaerobic bacteria, Shewanella putrefaciens, is first reported here in China. The experimental conditions were: 35℃ and pH = 7.0—7.4, corresponding to a physicochemical environments in which the sandstone-hosted in- terlayer oxidation-zone type uranium deposit formed in Northwest China’s Xinjiang. Bacteria adopted in the present experiment, Shewanella putrefaciens, occur extensively in natural envi- ronment. Our study shows that nano-crystal precipitates of uraninite quickly occurred on the surface of the cells within one week. It was found that the pitchblende was characterized by a random arrangement of uraninite nanocrystals (2—4 nm) in it, significantly different from natural pitchblende in which uraninite nanocrystals are arranged in order. Finally, a possible mechanism of uranium biomineralization by microorganisms in the deposits is discussed. Our investigation may supply a technical train of thoughts for bioremediation of nuclear-contaminated water envi- ronments and for underground dissolving extraction of the sandstone-hosted uranium ores.